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The real cost of charging my Model S at home

Discussion in 'Model S: Battery & Charging' started by WarrenInCA, Aug 5, 2015.

  1. WarrenInCA

    WarrenInCA Member

    Joined:
    Oct 4, 2014
    Messages:
    86
    Location:
    Scotts Valley, CA
    I took delivery of my P85D on 12/31/2014. For the first five months of 2015 I kept the same PG&E rate schedule I had prior to owning an electric car. That is, the tiered (E1) plan. Not surprising to me, my electric costs increased during this period.

    Then, beginning June 1st, I switched to the electric vehicle plan (EVA). Now looking at my data for June and July I see that my electric costs have gone down. But something very interesting also happened. When I compare June 2014 ($197) to June 2015 ($153), and July 2014 ($211) to July 2015 ($205), my electric costs have dropped so much that I am now paying less per month than I did last year - before I owned the Model S.

    In other words, charging my car at home is better than free!!
     
  2. Khatsalano

    Khatsalano Member

    Joined:
    Mar 21, 2015
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    648
    Location:
    San Mateo, CA
    If you can time your usage by running major appliances (dryer, washer, dishwasher, etc.) in the off-peak hours of the EV-A plan, it's very, very advantageous. Your pattern actually suggests that you would have been better off on the E-6 TOU plan before as opposed to E-1. I also recently switched to the EV-A plan the month I bought my Tesla. It was really good ... until I got solar. Now it's RIDICULOUSLY good.

    I'm selling to the grid when the sun is up at $0.22 - $0.43 / kWh. Then I'm buying back at night to charge my Tesla at $0.09 kWh. Pure pwnage.

    - K
     
  3. Eclectic

    Eclectic Member

    Joined:
    Nov 8, 2014
    Messages:
    294
    Location:
    San Francisco area
    We had a similar discovery when we went to EVA with our first P85 a few years ago. We moved as much of the discretionary electricity usage to the overnight period (i.e., pool filtering, dish and clothes washers, etc.) and the net effect was that while we used a ton more electricity, the EVA rate was so much lower that the total bill was no more than pre-P85 and in most cases, well below that amount. Lower electricity bill and no more $400/mo gasoline expense is a pretty compelling financial case.
     
  4. ohmman

    ohmman Maximum Plaid Member

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    Feb 13, 2014
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    4,836
    Location:
    North Bay, CA
    I also run on EV-A with solar. It's an obvious win in that case, but it's also a win without rooftop solar. If you have a pool, moving your filter pump schedule to overnight will drastically change things. I have pool solar, but in the summer I need to run it for, at most, an hour during daylight. During warmer spells, not at all.

    The downside is that when my true-up came last month, I had a $870 credit for the year despite having used 3+MWh over the course of the year. Obviously they don't cut me a check for that. It kind of stings leaving that money on the table, but I am still installing more solar because I'd rather be grid neutral.
     
  5. m6bigdog

    m6bigdog Member

    Joined:
    Mar 29, 2015
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    Location:
    San Ramon, CA
    Nothing could be finer than owning an MS with PV's on the roof!!
    My PV system is 7.3kW-ac and produces 1.5 MWh summer month peak. Last month we used 1.7 MWh's and we still got a $20 credit.
    I've had the solar for 2.5 years and so far it has generated 38 MWh's which turned my annual $3.5k+ PG&E bill into a $200-300 credit.

    I was surprised to see that with the EVA rate made charging the MS essentially free and didn't affect the overall NEM.
    Since PG&E has yet to provide a rate compassion page I made one from an Excel spreadsheet and it is obvious EVA is a little better than E-6, providing a 30-50% increase in the monthly NEM credit.

    Also, my solar was sized before I considered a MS and I was surprises that it didn't make economic sense to add more panels to compensate for the MS charging.
    I currently use 1.5-1.7mWh/mo. (summer A/C) but the solar only generated 1.5MWh peak and despite using 200-300 kWh more than the system generates I still see a $15-20 credit.
    It is pretty difficult to get a payback on installing PV panels when the annual average 1.2kWh/day production only generates $.048 NEM True-up return. That is a 57 year payback period if each PV panel ($4.00/watt) cost $1k installed.
    The original installation was a 6 year payback period and with charging the MS that has shortened up some.
    Yep, Solar and MS make a good pair!!
     
  6. ToddRLockwood

    ToddRLockwood Active Member

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    Sep 11, 2012
    Messages:
    1,263
    Location:
    Burlington, Vermont
    Another item worth noting regarding solar... Here in Vermont, where we do not have off-peak residential rates, I have found it advantageous to avoid charging my car during prime solar hours because I earn a higher kWh rate for the energy that I send to the grid than I pay for the energy I consume. My solar system gives priority to household loads, sending the energy there first, with the remainder being sent to the grid.
     
  7. m6bigdog

    m6bigdog Member

    Joined:
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    Location:
    San Ramon, CA
    Time of Use (TOU) is everything.
    However, given the Peak rate for us extends into the evening until 9 PM some of the potential solar earnings is lost.
    The Peak vs off-Peak rate for the PGE EVA rate (electric Vehicle charging) is 4 to 1 ($.427 vs $.0999) so if you can defer energy usage to off-Peak the solar generation during partial-Peak and Peak hours goes a long way.

    The only thing, there is only so much that can be deferred to the short overnight 8 hours of off-Peak period (11 PM to 7 AM). So...Oh, honey would you please stay up all night to wash and dry the clothes.. wouldn't go over very well in my house!!
    I only get 4-5 hours of solar generation during the Peak rate period the balance is during partial-Peak at 1/2 the Peak rate, during the morning, which takes a pretty good bite out of the potential earnings.
    And, I'm not going to sweat in my home to save money and retired people use A/C during the day so the A/C stays ON 24 hours!!
     
  8. WarrenInCA

    WarrenInCA Member

    Joined:
    Oct 4, 2014
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    Location:
    Scotts Valley, CA
    My forum post was picked up by an online publication. This might be my five minutes of fame!

    How To Have A Negative Charging Cost With An Electric Car - Gas 2
     
  9. Doug Darby

    Doug Darby Member

    Joined:
    Feb 2, 2015
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    65
    Location:
    United States
    Last month I put 1034 miles on my S85D and it cost me $17.34 for the power.
    No solar just inexpensive energy here in Texas where the energy industry is deregulated.
     

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